Method for scouring wool

ABSTRACT

A process and plant for scouring wool, wherein the wool is treated with a dry cleaning agent, such as for instance trichloroethylene or perchlorethylene, and used cleaning agent is separated from the wool and washed with a mixture of water and alcohol, the cleaning agent containing wool, grease being then separated from the water and alcohol and recovered in a solvent recovery low pressure and low temperature distillation apparatus.

United States Patent [72] Inventor Nell Seville Liversedge, England [21]Appl.No. 812,8!3 [22] Filed Apr. 2,1969 [45] Patented Nov. 9, 1971 [73]Assignee Thomas Burnley & Sons Limited Cleckheaton, Yorkshire, England[54] METHOD FOR SCOURING WOOL 3 Claims, 5 Drawing Figs.

[52] US. Cl 8/l39.l, 8/139, 8/142 511 Int. Cl D0lc3/00 [50] Field ofSearch 8/139, l39.l, 142

[56] References Cited UNITED STATES PATENTS 656,528 8/1900 Donard 8/139l,947,522 2/l934 Fluss 8/1391 2,655,428 l0/l953 Lundgren et al... 8/1392,7 l7,90l 9/1955 Norman 8/l39.l 2,925,639 2/1960 LaFleur 8/139 PrimaryExaminer-Mayer Weinblatt Atlorney-Holman & Stein PATENTEnunv 9 ml 3.6 19. l l 6 SHEET 1 OF 4 lcohol water to atmosphere METHOD son scoumnc WOOLThis invention relates to a process of scouring raw wool, to plant forthe performance of such process and a method based on the process forrecovering the cleaning agent used in the scouring process and producingpurified wool grease.

The invention thus consists in a process of scouring wool comprisingtreating wool with a dry cleaning agent, such as for instancetrichloroethylene or perchlorethylene, separating the used cleaningagent from the wool and washing the cleaning agent with a mixture ofwater and alcohol, separating the cleaning agent, containing woolgrease, from the water and alcohol, and recovering the cleaning agent ina solvent recovery low pressure and temperature distillation plant.

The invention further consists in wool scouring plant comprising atleast one cleaning machine and means for passing and recycling acleaning agent through the machine and is characterized by a solventrecovery low pressure and temperature distillation plant, which mayoperate in three stages and incorporate a thin film evaporator device.The use of such distillation plant materially avoids degradation of thewool grease.

During the phase separation dirt and water soluble impurities pass intothe water/alcohol phase and the wool grease remains in the solventphase.

The wool grease therefore passes into the still with the cleaning agentand is tapped off from the bottom of the still after distillation of thesolvent.

The purified solvent is reused for scouring further batches of raw wool.

One particular and at present preferred form of plant, to be describedonly by way of nonlimitative example is diagrammatically illustrated inthe accompanying drawings, in which FIG. 1 is a combined block and flowdiagram illustrating the plant components and their interrelation in theoperation of the process;

FIG. 2 illustrates the cooling water system;

FIG. 3 illustrates the hot water system;

FIGS. 4 and 5 are side elevation and plan views respectively of aconvenient plant layout.

Referring now to these drawings, there is shown a battery of eightPermac Bt'iwe dry cleaning machines 1, each having an associated 500gallon tank. These machines are coupled to an air cooling systemincluding an activated carbon adsorber 3 connected to the atmosphere andan air cooler 4 connected to a water separator (not shown). The cleaningmachines are also connected to a 3000 gallon buffer tank 5 forsolvent/grease mixture and also to a 3,000 gallon buffer tank for spentsolvent. The buffer tank 6 is in turn connected to a series of threedecanters 7A, 7B, 7C each of 3,000 gallon capacity and including amixing device. The decanters could be replaced by a centrifuge whichwould perform the same function. The outlets from these decanters areconnected to a steam operated evaporator 8 for the recovery ofalcohol/water mixture from the cleaning solvent. This evaporator mayhave a 450 sq.ft. exchange surface and include a stirrer. The evaporator8 is connected to a double roller drier 9 for drying dirt and suintmixture and to a condenser and receiver 10 for condensing alcohol/watermixture.

FIGS. 4 and 5 show a solvent storage tank 11 of 3,000 gallon capacity,and there is also an alcohol storage tank not shown of 500 galloncapacity.

FIGS. 1, 4 and 5 also show a first stage evaporator 13 including afalling film evaporator. In FIG. 1 there is also shown a first stagesteam ejector 14, a first stage condenser 15, a second stage evaporator16 of the wiped thin film type, a second stage tubular condenser 17, athird stage wiped thin film evaporator 18 and a thermocompressor 19including intermediate condenser 19 and steam ejector.

FIG. 2 shows a cooling system including two packaged water chillers 20and a packaged cooling tower 21.

FIG. 3 shows a hot water system 22 to provide process water at 60f-65PC.

The mode of use of the plant as above described is as follows:

The scouring of the wool takes place in the dry cleaning machines 1; thecycle time for each load (208 pounds of dirty wool) is 20 minutesincluding loading, two washes, drying, cooling and unloading. It isfound to be most economical to lose one gallon of solvent (e.g.perchlorethylene) per 600 lbs. of clean wool as the excessive steamconsumption for further drying would counterbalance the additional gainin solvent. The loss of solvent carried along with the cooling air ishowever cut to a minimum by using the chilled water cooler and theactivated carbon adsorption plant. The spent solvent from the first washcontaining the suint, dirt and grease is pumped into the buffer tank 6,whereas the solvent from the second wash is pumped into the tanks 2which are associated with the washing machines to be used for the firstwash of the next load.

From the buffer tank 6 the spent solvent is continuously mixed with awater/isopropyl alcohol mixture which dissolves the suint and dirt,forming a suspension which is separated from the solvent/grease mixturein the decanters 7A, 7B, 7C.

The water/alcohol mixture containing suint and dirt is led to theevaporator 8 which recovers the alcohol and water by distillation. Thebottom stream from the evaporator 8 is fed on to the double roller drier9 which recovers the remainder of the alcohol and water and dischargesthe suint and dirt as a dry powder. This dry powder may be usefullyemployed in agriculature.

The solvent containing the grease is fed from the last decanter 7C intothe other buffer tank 5 where it is mixed with grease-free solventreturning from the solvent recovery part of the plant. To minimize thesize of the recovery section the concentration of grease in this tankshould be kept as high as possible. A grease content of about 3 percentto about 7 percent and preferably of 5 percent by weight has been foundacceptable to the scouring process.

The bufier tank 5 is bled continuously to the solvent recovery sectionwhich is in three stages. In the first stage the bulk of the solvent isrecovered in the tubular evaporator 13 under a pressure of about 25 mm.Hg Abs. and the preconcentrated grease is led to the second stage whichis the agitated thin film evaporator 16. Here the preconcentrated greaseflows over a heated wall in a thin film which is being agitated by' arotor under a pressure of about 12 mm. Hg Abs. Further concentrationtakes place, while the solvent is condensed and recovered in the tubularcondenser 17. The third stage is similar to the second stage butoperates at even lower pressure e.g. about 2 mm. Hg Abs. and includessteam stripping which ensures the removal of the last traces of solventand some lower boiling impurities of the grease. Wool grease of highquality is discharged from the third stage ready to be packed and sold.In order to condense the solvent and the stripping steam from the thirdstage the thermocompressor 19 is used. The resulting solvent/ watermixture is consequently separated in a decanter before the solvent ispassed back to the buffer tank 5. In order to avoid degradation of thewool grease during the solvent recovery stage hot water is used as theheating medium throughout the process.

Each cleaning machine has a button trap. and an optionally associatedfilter unit through which the cleaning solvent is pumped before it isreturned to the wool in the drum of the machine. Each filter unit is ofthe diatomaceous earth type and filters down to 4 microns. It isessential periodically to clean the filter units and this is done bypumping clean grease laden solvent from the buffer tank 5 in reversedirection, thus causing dirt and filter powder to be washed away andcarried to the buffer tank 6. No additives are normally required.

The drums of the cleaning machines are preferably lined with perforatedfabric.

By use of the plant as specifically described, 5,000 pounds of dirtywool (e.g. 53 percent wool, 15 percent grease, 20 percent suint and dirtand 12 percent moisture) can be treated per hour with about 3,000gallons of perchlorethylene to yield 750 pounds per hour of highlypurified grease.

The invention is applicable to most chlorinated hydrocarben dry cleaningagents with or without addition of alcohols, e.g. 5 percent isobutylalcohol or cyclohexane.

perchlorethylene under cooled conditions, separating the used cleaningagent from the wool and continuously washing it with a mixture of waterand a lower alkyl monohydric alcohol, recovering the alcohol and waterby distillation and recovering the cleaning agent by multistage lowpressure and temperature distillation.

3. A process of scouring wool as set forth in claim 1 wherein thecleaning agent is recovered in three stages under progressively lowerpressures, the second of said stages involving thin film evaporation andthe third stage including steam stripping.

2. A process of scouring wool and recovering wool grease comprising treating wool with a dry cleaning agent selected from the group consisting of trichloroethylene or perchlorethylene under cooled conditions, separating the used cleaning agent from the wool and continuously washing it with a mixture of water and a lower alkyl monohydric alcohol, recovering the alcohol and water by distillation and recovering the cleaning agent by multistage low pressure and temperature distillation.
 3. A process of scouring wool as set forth in claim 1 wherein the cleaning agent is recovered in three stages under progressively lower pressures, the second of said stages involving thin film evaporation and the third stage including steam stripping. 